In high pressure water blast cleaning, one type of spray gun that is used is a shut-off style which automatically closes when there is no force on an operating lever that controls a valve in the gun. When the valve closes, water is re-routed at high pressure from the blast gun to a regulator valve at the pump. The regulator valve reduces the pressure to near atmospheric, and the water is fed to the supply tank or other remote location. A major drawback of the system is that high pressure remains in the line between the blast gun and the regulator at all times while the pump is running, even though the blast gun control valve is closed. This can create a dangerous situation in the event of hose failure, or where the operator is unaware that high pressure is present at the blast gun.
Where a regulator valve is employed, the pump is running continuously at a constant speed regardless of whether the gun operator is blasting or not, and supplies a constant line pressure that is independent of flow. Most regulators include a hardened valve element such as a ball that cooperates with a seat in a manner such that the valve is pressed against the seat with a very high force which offsets the force due to line pressure acting on the exposed area of the valve element. The regulating force typically is produced by a large, heavy coil spring or a stack of Belville washers which require a wrench for adjustment. Although straightforward in design, another major drawback is that water is jetted constantly across the seat and valve at operating pressure while the pump is running, even though blasting operations have been suspended. This causes excessive regulator and valve element wear, as well as wear on other parts that are exposed to a high velocity stream of water downstream of the valve. Such parts can require considerable time and expense to replace, particularly in the field. Another problem with such regulators is that as noted above they cannot be adjusted by hand due to the large hydraulic force applied to the valve which is offset by equally large spring forces. As an example, the hydraulic force can be in the range of from 4,000 to 6,000 lbs. at an operating pressure of 15,000 psi.
Although efforts have been made to use nitrogen gas in a large pressure cylinder to supply the high reactor force needed on the regulator valve, the system requires an additional hand adjustable regulator at the cylinder to maintain a constant pressure. Thus, the system is very large, heavy and expensive because at the physical size of the nitrogen bottle, and becomes nonfunctional when the nitrogen supply is exhausted.
An object of the present invention is to provide a new and improved pressure regulator for a water blast system that obviates the above-mentioned short-comings.
Another object of the present invention is to provide a new and improved pressure regulator of the type described which can be easily adjusted by hand so that no tools or wrenches are required.
Yet another object of the present invention is to provide a new and improved regulator of the type described where all wear parts are housed and contained in an easily replaceable cartridge.
Still another object of the present invention is to provide a new and improved regulator that has compact size and is light-weight to permit easy installation at any point in a water blast system.
Another object of the present invention is to provide a new and improved pressure regulator for a water blast system where the valve cartridge includes a bleed-down orifice to purge the blast line after the pump has been shut down.